In a Long Term Evolution system, based on the resident eNB of the UE (User Equipment), switch is divided into intra-eNB switch and inter-eNB switch. Wherein, intra-eNB switch means that the source cell and the target cell involved in the switch are located in the same eNB; inter-eNB switch means that the source cell and the target cell involved in the switch are located in different eNBs. Based on whether the carrier frequency of the cell before and after switch changes or not, switch is also divided into intra-frequency switch and inter-frequency switch. Based on whether the wireless technique used by the UE before and after switch changes or not, switch is also divided into intra-LTE system switch and inter-LTE system switch. Based on the whether participation of the EPC (Evolved Packet Core) is needed to implement the switch, or based on whether the switch occurs at the S1 interface or the X2 interface, inter-eNB switch is also divided into X2 interface switch and S2 interface switch. Based on whether the S-GW changes during the switch process, switch is also divided into switch with changed S-GW and switch with unchanged S-GW.
The EPC has two core device entities, one being MME (Mobility Management Entity), which is responsible for processing of control-plane signaling; the other one being S-GW, which is responsible for processing of user-plane signaling, and for management of the tunnel (GTP-U, GPRS Tunnelling Protocol User Plane) of the user in the GPRS (General Packet Radio Service). When a user establishes a call, at least one GTP-U tunnel is established between the eNB and S-GW, and one end of the tunnel is on the user plane entity of the eNB, while the other end is on the S-GW. If the user has an inter-S-GW switch, the GTP-U established in the user call needs to be transferred to the new S-GW.
The connection relationships between UE, eNB, MME and S-GW are as shown in FIG. 1, wherein MME and S-GW are two separate network element entities, the interface between the eNB and MME is called as an S1-MME, and the interface between the eNB and S-GW is called as an S1-U interface. The interface between the UE and the eNB is called as a Un interface. The interface between eNBs is called as an X2 interface, which is a logic interface. The MME and S-GW may also be integrated into one physical network element entity, in which case, the interface between the eNB and the MME is collectively called as an S1 interface (not shown in the figure).
The GTP-U tunnel is managed through a pair of TEIDs (Tunnel End Point Identifiers) and an IP (Internet Protocol) address. Wherein, the TEID pair is used to identify a GTP-U tunnel, and the IP address is used to point out the IP route under the service carried out through the GTP-U tunnel, i.e., the transmission layer address. The TEID at the eNB side in the TEID pair is distributed by the eNB, and a GTP-U entity is established on the user plane; the TEID at the S-GW side in the TEID pair is distributed by the MME (may also be distributed by the S-GW), and a GTP-U entity is established at S-GW side.
When a switch occurs, if the S-GW where the UE is located needs to change, the MME needs to establish a new GTP-U entity using a new TEID on the target S-GW, and deletes the old GTP-U entity on the source-side S-GW. Similarly, when an inter-eNB switch occurs, a new TEID needs to be established for the UE at the target-side eNB, and the TEID of the corresponding service of the user is deleted on the source-side eNB that is switched. During the switch process, the eNB needs to inform the MME of the change of the TEID at the eNB side through a PATH SWITCH REQUEST message, and then inform the S-GW. Similarly, the MME needs to inform the eNB of the change of the TEID at the MME side through a PATH SWITCH REQUEST ACKNOWLEDGE message.
The structure inside the eNB is as shown in FIG. 2, including a control-plane sub-system, a user-plane sub-system and a route sub-system. Wherein, the control-plane sub-system processes the control-plane signaling, the user-plane sub-system processes the user-plane related signaling, and the route sub-system processes the signaling route and data route through the S1 interface. For the uplink data sent by the eNB to the S-GW, the route sub-system needs to find the next-hop (i.e., the next node) MAC address of the data according to an IP routing table maintained by the route sub-system, and the MAC address is generally the MAC address of the receiving net port of the S-GW network element, or, when there is an intermediate router, is the MAC address of the router.
When the switch between eNBs is an X2 switch, the eNB sends a PATH SWITCH REQUEST message to the MME to request the MME to switch the downlink GTP-U tunnel; after completing the GTP-U tunnel switch of the S-GW, the MME sends a PATH SWITCH REQUEST ACKNOWLEDGE message to the eNB; after the eNB receives the message, the TEID carried in the message needs to be updated if the S-GW has changed.
The method for the eNB to update the TEID in the related art is that the control-plane sub-system notifies the user-plane sub-system to modify the TEID, and meanwhile notifies the route sub-system to modify the IP routing table information. Since there is a time difference between the two operations, packet loss is caused to happen to the uplink data. For example, if the routing table is updated firstly, it may cause the data on the old TEID to be unable to find the uplink route (i.e., unable to identify the updated routing table), thus causing data loss; if the TEID is updated firstly, it will cause the data on the new TEID to be unable to find the uplink route (i.e., unable to identify the old routing table), thus causing data loss. Data loss will cause the application layer to retransmit the data, thus increasing the time delay of data transmission, and decreasing the effective throughput of the system, and hence affecting the service experience of the user during switch.
Therefore, a new and efficient method and system are needed to solve the problem of the uplink data packet loss during switch due to the time difference existing between the update to the Tunnel Endpoint Identifier (TEID) and the routing table by the eNB when inter-eNB switch is performed via X2 and the S-GW has changed.